Shims are commonly used in fitting and assembling parts and subassemblies in order to compensate for dimensional variations. In the aircraft industry, shims are used extensively in fitting and joining fuselage sections, and in attaching wings and tail assemblies (vertical fin and horizontal stabilizer assemblies) to the fuselage. The shims, sometimes referred to as fillers, are used to fill voids between the joined assemblies which may be caused by tolerance build up in parts. The use of shims to fill voids between mating surfaces on part assemblies results in a more structurally sound aircraft. Shims are also used to bring parts into proper alignment.
Design and fabrication of unique shims for each aircraft can be a time consuming and labor intensive process. A skilled technician must manually measure and record each void in order to determine the dimensions and shape of a particular shim that will fill the void. The recorded dimensions are then sent to a machine shop where the shim is fabricated.
The shim design and installation process described above may materially slow down aircraft assembly, especially where the assemblies are manufactured in different geographic locations and are shipped to a final assembly location. This is due, in part, to the fact that the shims cannot be designed and manufactured until the assemblies are fitted together at the final assembly destination so that the size and shape of the voids can be determined.
Efforts have been made to reduce the time required for determining shim dimensions as exemplified in U.S. Pat. No. 6,618,505 issued Sep. 9, 2003 and assigned to the Boeing Company. This prior patent discloses a method and apparatus for determining the dimension of a shim, using digital photogrammetry to measure the profile of the voids requiring shims. The shim dimensions are calculated based on the void profile measurements referenced against an engineering standard defining an ideal fit between the assemblies. While this prior process reduces the time required for shim design, further efficiency improvements are possible.
Accordingly, a need exists for a method for fitting and joining part assemblies in which the shims are automatically designed and fabricated without the need for physically fitting the part assemblies to determine the location and profile of potential voids. Embodiments of the disclosure are directed towards satisfying this need.